• Title/Summary/Keyword: 재액화

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Process Design and Analysis of BOG Re-liquefaction System with Pre-liquefaction of NGL (NGL 분리식 BOG 재액화 공정 고안 및 해석)

  • Yun, Sang-Kook
    • Journal of the Korean Institute of Gas
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    • v.19 no.3
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    • pp.32-37
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    • 2015
  • The boil-off-gases(BOG) in cryogenic LNG storage tanks are generating continuously due to the heat leakage and need to be re-liquefied by the effective way. As the present method to reliquefy BOG is using LNG cold energy to be supplied after low pressure primary pump, the demand of LNG flow rate should be over 10 times of BOG produced rate to reliquefy it. This research invented new effective re-liquefaction system having only 3~4 times of LNG flow rate against unit BOG, that the pre-liquefaction process of NGL and the use of high pressure LNG cold energy after secondary pump. By the analysis, it could be high efficient reliquefying system for all amount of BOG treatment even during the summer time, and improvement of operation safety and efficiency of LNG terminal.

Characteristics of boil-off-gas partial re-liquefaction systems in LNG ships (LNG선박용 BOG 부분재액화 시스템 특성 연구)

  • Yun, Sang-Kook
    • Journal of Advanced Marine Engineering and Technology
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    • v.40 no.3
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    • pp.174-179
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    • 2016
  • To protect the ocean environment, the use of liquefied natural gas (LNG) carriers, bunkering ships, and fueled ships is increasing. Recently, Korean shipbuilders have developed and supplied a partial reliquefaction facility for boil-off-gas (BOG). Despite reasonable insulation, heat leakage in vessel storage tanks causes LNG to be continuously evaporated as BOG. This research analyzed the maximum liquid yield rate for various partial reliquefaction systems (PRS) and considered related factors affecting yields. The results showed a liquid yield of 48.7% from an indirect PRS system (heat exchanges between cold flash gas and compressed natural gas), and 41% from a direct PRS system (BOG is mixed with flash gas and discharged from a liquid-vapor separator). The primary factor affecting liquid yield was heat exchanger effectiveness; the exchanger's efficiency and insulation characteristics directly affect the performance of BOG reliquefaction systems.

Design and Assessment of Reliquefaction System According to Boil Off Gas Reliquefaction Rate of Liquefied Hydrogen Carrier (액화수소 운반선의 증발가스 재액화 비율에 따른 재액화 시스템의 설계 및 평가)

  • Cho, Wook-Rae;Lee, Hyun-Yong;Ryu, Bo-Rim;Kang, Ho-Keun
    • Journal of Navigation and Port Research
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    • v.44 no.4
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    • pp.283-290
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    • 2020
  • BOG (Boil Off Gas) generation is unavoidable in the liquefied hydrogen carrier, and proper measures are necessary to prevent pressure problems inside the cargo tank. The BOG can be used as propulsion fuel for ships, and the remaining parts used for propulsion must be effectively managed, such as in the form of reliquefying or burning. This study proposes an BOG reliquefaction system optimized for a 160,000 m3 liquefied hydrogen carrier with a hydrogen propulsion system. The system comprises a hydrogen compression and helium refrigerant section, and increases the efficiency by effectively using the cold energy of the BOG discharged from the cargo tank. In this study, the system was evaluated through the exergy efficiency and SEC (Specific Energy Consumption) analysis according to the rate of the reliquefaction of the BOG while the hydrogen BOG with a supply temperature of -220℃ entered the reliquefaction system. As a result, it showed SEC of 4.11 kWh/kgLH2 and exergy efficiency of 60.1% at the rate of reliquefaction of 20%. And the parametric study of the effects of varying the hydrogen compression pressure, inlet temperature of the hydrogen expander, and the feed hydrogen temperature was conducted.

The Experimental Study of Insulation Structure for BOG Re-liquefaction Drum (증발가스 재액화 드럼의 단열구조에 관한 실험적 연구)

  • Kim, Ik-Soo;Jung, Young-Jun
    • Journal of the Korean Institute of Gas
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    • v.25 no.1
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    • pp.7-13
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    • 2021
  • The re-liquefaction drum is a product that installed spray nozzles at the top to directly spray overcooled LNG into evaporative gas and installed demistors to facilitate gas separation, which was developed to increase the re-liquidity efficiency of small scale re-liquefaction facilities. In the hydrostatic test of the drum, no leakage occurred even at a pressure of 1.5 times the design pressure, but during the BOR(Boil Off Rate) test, the bolt loosening occurred due to contraction and expansion by temperature change. For the continued use of the product, insulation construction on flange connections was developed to enable detachment and attachment, and the comparison of heat load with existing insulation confirmed that it was very small compared to the inlet flow rate in the drum.

A Study on the Improvement of LNGC Re-liquefaction System (LNG선 재액화 시스템의 성능 개선에 관한 연구)

  • Oh, Cheol;Song, Young-Uk
    • Journal of Navigation and Port Research
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    • v.33 no.10
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    • pp.659-664
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    • 2009
  • LNG carriers have, up to 2006, mainly been driven by steam turbines. The Boil-Off Gas from the LNG cargo tanks has so far been used as fuel. This is a costly solution that requires special skills during construction and operation. Alternative propulsion systems offer far better fuel economical efficiency than steam turbines. Instead of previous practice using Boil-Off Gas as a fuel, the Re-liquefaction system establishes a solution to liquefy the Boil-Off Gas and return the LNG to the cargo tanks. This Re-liquefaction of Boil-Off Gases on LNG carriers results in increased cargo deliveries and allows owners and operators to choose the most optimum propulsion system. In this study, thermodynamic cycle analysis has been performed on two type of LNG Re-liquefaction system which was designed and adopted for the Q-Flex(216,000$m^3$) and Q-Max(266,000$m^3$) LNG carrier under construction at Korea ship yards and variable key factor was simulated to compare efficiency, power and nitrogen consumption of each Re-liquefaction system.

Study of LNG Reliquefaction Process in LNG Carriers (LNG 선박에서 천연가스 재액화공정의 재액화량에 관한 연구)

  • Ko, Byoung-Seok;Kim, Bum-Su;Lee, Heon-Seok;Kang, Yun-Jin;Kim, Min-Seop;Ko, Jae-Wook
    • Journal of the Korean Institute of Gas
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    • v.14 no.1
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    • pp.21-27
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    • 2010
  • In the past vaporized gases from a carrier were burned or used for fuel. Due to the movement of bigger LNG carriers and using diesel engine, it is limited that ways of deposing vaporizes gases from the carrier by the act of environment. For getting over the problem, a reliquefaction process is considered. Even though the reliquefaction process was created to three generation process, it has been researched and developed to optimize the process. Basically the reliquefaction process is compartmentalized into Reverse Brayton Cycle System and Claude Cycle System. This research is focused on the reliquefaction efficiency with the systems and changing equipments arrangement by using HYSYS. The result could be use for a design of a reliquefaction process.

An Optimization Study on the Reliquefaction of Boil-Off Gas from Liquefied Petroleum Gas Storage Tank (액화석유가스 저장탱크로부터 발생하는 증발가스 재액화 공정의 최적화에 대한 연구)

  • NOH, SANGGYUN
    • Transactions of the Korean hydrogen and new energy society
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    • v.30 no.5
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    • pp.395-400
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    • 2019
  • Comparative studies between single- and two-stage refrigeration cycle using propane as a refrigerant have been performed for a vapor recompression refrigeration cycle. PRO/II with PROVISION release 10.2 from AVEVA company was used, and the Soave-Redlich-Kwong equation of state model with Twu's alpha function was selected for the modeling and optimization of the refrigeration cycle for the reliquefaction of BOG coming out from the LPG storage tank. In two-stage refrigeraton cycle, 24.8% of compressor power was reduced compared to that of single-stage refrigeration cycle through the optimization works.

Basic Design of 36 MTD Class Natural Gas BOG Re-Liquefaction System (36 MTD급 천연가스 BOG 재액화 플랜트 기본설계)

  • Ko, Junseok;Park, Seong-Je;Kim, Ki-Duck;Hong, Yong-Ju;Koh, Deuk-Yong;Kim, Hyobong;Yeom, Hankil
    • Transactions of the KSME C: Technology and Education
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    • v.1 no.1
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    • pp.99-105
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    • 2013
  • In this paper, we carried out the basic design of 36 MTD natural gas BOG re-liquefaction system to recover the generated natural gas during performance test of LNG pump and natural gas compressor. The re-liquefaction process of natural gas is designed to have 1500 kg/h of liquefaction rate with reverse Brayton refrigeration cycle. With the designed process, the variation of liquefaction rate is calculated for various inlet conditions of feed gas. From results, the liquefaction rate is more sensitive for inlet temperature than gas composition. The specifications of equipments such as gas blower, natural gas compressor, cryogenic heat exchanger and nitrogen compander are determined on the basis of the designed process. The requirement of power consumption and cooling water are also determined through the basic design.

Thermodynamic Analysis of Re-liquefaction Cycle of LNG Boil-off Gas (LNG 증발기체의 재액화 사이클에 대한 열역학 해석)

  • Chin, Young-Wook;Moon, Jeong-Woo;Lee, Yoon-Pyo;Chang, Ho-Myung
    • Korean Journal of Air-Conditioning and Refrigeration Engineering
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    • v.19 no.7
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    • pp.485-490
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    • 2007
  • The LNG BOG re-liquefaction system for LNG carriers was designed based on the Claude refrigeration cycle and the thermodynamic analysis was carried out in order to find the design point of the three heat exchangers constituting the system. The thermodynamic analysis revealed that the system state could be defined by the three cold endpoint temperatures of the three-pass heat exchanger. Hence the iso-lines of the specific liquefaction work, taken as the performance indicator, were presented in terms of those three temperatures and discussed. The system was found most economical when those three temperatures approached a single temperature of $-140^{\circ}C$ and thus this system state could be taken as the design point for the heat exchangers.